Controlling Common Mullein in Pastures

Controlling Common Mullein in Pastures

May 15, 2009

Common mullein (Verbascim thapsus) is a weed species that's increasing in northeast Nebraska's rangeland, woodland, and pastures. It is a biennial plant that reproduces only by seeds, but it is a prolific seed producer. The taproot of this species can access soil moisture from a deeper profile at a much better rate than fibrous roots of pasture grasses, giving it a competitive advantage, especially in dry years.

Figure 1. Common mullein (Verbascim thapsus) in a Nebraska pasture.

Identification

Common mullein usually starts growing sparsely as individual plants and then spreads. A cluster of leaves, commonly known as a rosette, with a thick hair cover is a distinct identifying feature of this species. Other identifying characteristics include:

Stem is woolly, erect, 2-6 feet tall, and without branches.

Leaves are opposite, elliptic to ovate.

Overall growth depends on the amount and timing of rainfall.

Produces yellowish flowers in June and July.

Low palatability and no feed value to livestock.

Heavy stands can reduce grass production as much as 50%, especially in dry years.

Control

The best strategy is to control common mullein while the population density is low. Plant numbers can easily expand from a few to hundreds per acre in just a couple years due to prolific seed production.

Mechanical Control. Sparse populations can be controlled by mechanical removal using a spade or shovel in late April and early May. Individual plants can be dug out or cut just at the soil surfaces as long as the whole rosette is removed. Single mowing of new 1-2 foot tall plants can reduce population and seed production for the season, especially in dry years.

Chemical Control. Herbicides also can be effective in providing season long control; however, be aware that the thick wooly coat of hairs on the leaves can reduce herbicide uptake and control.

Apply herbicide when the rosette has 6-12 leaves and before the stem starts to grow, which is usually in May. Effective herbicides and their rates per acre include: Grazon P+D (3-4 pints/acre), Cimarron (0.75-1 oz/acre), and a three-way-mix of Cimarron (0.5 oz) with Glean (0.5 oz) and RangeStar (32 oz). Make sure to use enough of an additives such as crop oil at 1-2 quarts/acre to help the herbicide penetrate the thick wooly coat.